1. Field
The present disclosure is directed to a method and apparatus for charging devices using a multiple port power supply. More particularly, the present disclosure is directed to providing cable compensation when charging devices using a multiple port power supply.
2. Introduction
Presently, power supplies are used to charge electronic devices. To charge a device, the device is connected to a power supply device charging port using a connection cable. The power supply then provides power through the connection cable to charge the device.
Unfortunately, the connection cable adversely affects device charging because it causes a voltage drop from the power supply to the device. The voltage drop causes a problem because both a power supply and device power management circuitry have minimum and maximum voltage charging requirements and these voltage requirements are adversely affected by the voltage drop. For example, Universal Serial Bus (USB) specifications require specific minimum and maximum power supply voltages. However, a USB connection cable that uses 60 inch 24 gauge wire causes an 180 mV per amp drop between the power supply and the device. If the voltage drop is not accounted for, the connection cable causes power supply voltage to fall outside of the voltage requirements. Other power supply specifications have other requirements, such as other minimum and maximum voltage charging requirements. Furthermore, other connection cables and other connection cable lengths and sizes cause different voltage drops.
The voltage drop problem gets worse if multiple devices are connected to a single power supply. This is because the voltage drop changes when multiple devices are connected and the power supply is unable to account for different voltage drops.
Thus, there is a need for a method and apparatus for charging devices using a multiple port power supply.